1. Field of the Invention
The present invention relates to a work mounting apparatus or complement mounting apparatus for mounting an IC chip or some other electronic component, as a work, on a printed board.
2. Description of the Related Art
As used herein, "work" refers to a component or element which is to be retrieved from a supply location and to be mounted upon a device or an element of a device, such as a printed board, by a component mounting apparatus or work mounting apparatus.
A work mounting apparatus of this type is disclosed in Published Unexamined Japanese Patent Application No. 62-114290, for example. This conventional apparatus comprises a rotating table and a plurality of suction heads arranged at predetermined intervals on the outer peripheral edge of the table. Each suction head is capable of up-and-down motion.
A workbench is disposed under the rotating table, and a component or work supply section and a component or work mounting section are arranged on the workbench at a distance from each other in the circumferential direction of the table. A plurality of work feeders or component feeders are radially arranged in the supply section, while a printed board is disposed in the mounting section.
When one of the suction heads is positioned in one of the work feeders of the supply section as the table rotates, the rotation of the table is stopped. In this state, the suction head is lowered, receives a work from the work feeder by suction, and is then raised to its original position. When the rotation of the table is restarted, thereafter, the suction head is transferred from the supply section to the mounting section. When the suction head is positioned in the mounting section, the rotation of the table is stopped again. In this state, the suction head is lowered again, whereupon the work is released from the suction, so that it is mounted on the printed board in the mounting section.
According to the work mounting apparatus described above, the rotation of the table must be stopped every time the suction head is move up or down, that is, every time the work is received or mounted in the supply or mounting section. In other words, the rotation of the table and the operation of the suction head are performed intermittently, so that the tact time cannot be shortened, and therefore, the work mounting efficiency is low.
In these circumstances, there is a demand for continuous-type work mounting apparatuses in which works can be received and mounted without stopping the rotation of the table.
In one such continuous-type mounting apparatus, for example, a continuously rotatable drum, which is used in place of the rotating table, is surrounded by a plurality of work heads which repeat up-and-down motion as they turn. More specifically, the work heads turn around a turning axis which extends in the radial direction of the rotating drum, and their respective postures are kept fixed during the turning motion.
Thus, if a suction nozzle is provided protruding downward from each work head, it can repeat up-and-down motion while moving in the circumferential direction of the rotating drum, as the drum rotates and as the work head turns.
If the turning speed and turning direction of the work head are properly set with respect to the peripheral speed of the rotating drum, moreover, the relative speed of the suction nozzle with respect to the supply and mounting sections, that is, the ground speed, can be reduced substantially to zero when the suction nozzle lowers so that the supply and mounting sections come closest to each other. Even while the rotating drum is being continuously rotated, therefore, the suction nozzle of the work head can securely receive a work from one of the work feeders of the supply section by suction, and then mount the received work head on a printed board in the mounting section.
In order to improve the work mounting efficiency of the continuous-type work mounting apparatus described above, the time required for the movement of the work head from the supply section to the mounting section must be shortened. This can be attained by only increasing the peripheral speed of the rotating drum. If the peripheral speed of the drum is increased, however, the ground speed of the suction nozzle, with respect to the supply and mounting sections, cannot be reduced to zero in the aforesaid manner unless the turning speed of the work head is increased correspondingly.
If the turning speed of the work head is increased, moreover, the cycle of the up-and-down motion of the suction nozzle is inevitably shortened. This indicates that the suction nozzle is frequently moved toward and away from the workbench during the process in which the nozzle moves from the work feeder toward the printed board. In the supply section on the workbench, therefore, the suction nozzle or the work thereon may possibly interfere with the other work feeders or devices on the workbench. This imposes restrictions on the arrangement of the work feeders and various other devices on the workbench.